A multi-frequency differential antenna with common mode rejection

Abstract

This invention discloses a multi-frequency differential antenna with common-mode suppression, belonging to the field of wireless communication antenna technology. It employs a single-layer dielectric substrate, with an n-type differential microstrip feed line on the upper surface and a metal ground plane with a specially etched structure on the lower surface. The ground plane has a rectangular defect symmetrical about the central axis and two sets of zigzag slots; the rectangular defect consists of three segments A, B, and C connected sequentially; the zigzag slots consist of three vertically connected slots, with their inner ends connected to the two ends of segment C of the rectangular defect. Through the synergistic effect of differential feed excitation and the etched structure of the ground plane, resonance is generated in multiple frequency bands, and common-mode interference is effectively suppressed using an odd-symmetric electric field distribution, achieving a common-mode reflection coefficient of less than -2dB across the entire frequency band. This invention has a compact structure, low profile, and is easy to manufacture, making it suitable for miniaturized multi-frequency communication equipment.

Description

Technical Field

[0001] This invention relates to a multi-frequency differential antenna with common-mode suppression, belonging to the field of wireless communication antenna technology. Background Technology

[0002] With the rapid development of wireless communication technology, technologies such as Wireless Local Area Networks (WLAN) and 5G mobile communication have been widely applied in fields such as smart terminals, IoT devices, and industrial control. These devices place stringent requirements on the multi-band operating capability, anti-interference performance, and integration level of antennas. On the one hand, antennas need to possess multi-band resonant characteristics to enable a single device to cover communication needs in multiple scenarios. On the other hand, with the trend towards miniaturization and thinner designs, antennas need to meet the design requirements of compact structure, low profile, and low cost, and must effectively resist common-mode interference in complex electromagnetic environments to ensure the stability and reliability of signal transmission.

[0003] Existing multi-frequency antenna implementation schemes mainly suffer from the following technical defects: First, traditional multi-frequency antennas often employ multi-layer dielectric substrate stacking, multi-radiating element cascade, or stub-loaded structures, resulting in large antenna size, complex structure, and cumbersome manufacturing processes. This not only increases manufacturing costs but also makes it difficult to adapt to the integration requirements of miniaturized terminal devices. Second, some multi-frequency antennas use single-ended feeding, which has weak common-mode interference suppression capabilities. In complex electromagnetic environments, they are easily affected by common-mode signals such as power supply noise and external electromagnetic radiation, leading to signal distortion, reduced radiation efficiency, and seriously affecting communication quality. Third, although a few differential structure multi-frequency antennas have certain common-mode suppression capabilities, this is usually achieved by sacrificing the number of frequency bands or optimizing the complexity of the feeding network. It is difficult to simultaneously achieve the design goals of multi-band coverage, high common-mode rejection ratio, and structural simplification, thus limiting their engineering applications.

[0004] Therefore, developing a differential antenna that is compact, low-profile, easy to manufacture, and capable of simultaneously achieving multi-band resonance and efficient common-mode suppression has become an urgent technical problem to be solved in the field of wireless communication antennas, and is of great significance to promoting the development of miniaturized and high-performance communication equipment. Summary of the Invention

[0005] In order to solve the above-mentioned technical problems, this invention discloses a multi-frequency differential antenna with common-mode suppression, which has the advantages of compact structure, low profile, simple processing, and the ability to simultaneously achieve multi-band resonance and efficient common-mode suppression. It is of great significance to promote the development of miniaturized and high-performance communication equipment.

[0006] The technical solution adopted in this invention is as follows: A multi-frequency differential antenna with common-mode suppression includes a differential microstrip feed line, a metal ground plane, and a single-layer dielectric substrate; The differential microstrip feed line and the metal ground plane are located on the upper and lower surfaces of the single-layer dielectric substrate, respectively. The metal ground plane has zigzag gaps and rectangular defects; wherein the rectangular defects include rectangular defect segments A, B and C that are connected in sequence and symmetrical about the central axis a; The zigzag gaps are provided in two sets, and the two sets of zigzag gaps are symmetrical about the central axis a; the inner ends of the two sets of zigzag gaps are respectively connected to the two ends of the rectangular defect segment C; The differential microstrip feed line has an n-type structure; the rectangular defect segment A is located in the projection of the region enclosed by the n-type structure onto the metal ground plane.

[0007] Furthermore, the differential microstrip feed line includes a first metal patch, a second metal patch, and a third metal patch; wherein the second metal patch and the third metal patch are parallel to each other, and the first metal patch is connected to the same side of the second metal patch and the third metal patch to form an n-shaped structure, with the opening of the n-shaped structure facing outward.

[0008] Furthermore, the inner end of rectangular defect segment B is connected to the middle of the long side of rectangular defect segment C, and the outer end of rectangular defect segment B is connected to the middle of the wide side of rectangular defect segment A. Rectangular defect segment B and rectangular defect segment C are perpendicular to each other, and the long side of rectangular defect segment C and the wide side of rectangular defect segment A are parallel to each other.

[0009] Furthermore, the zigzag gap includes gap a, gap b, and gap c connected in sequence; gap a is connected to the rectangular defect segment C and is perpendicular to each other; Slits a and b are perpendicular to each other; slits b and c are perpendicular to each other; slits a and c are both parallel to the central axis a, and the distance between slit c and the central axis a is less than the distance between slit a and the central axis a.

[0010] Furthermore, the single-layer dielectric substrate uses FR4 with a dielectric constant of 4.4 and a loss factor of 0.02.

[0011] Compared with the prior art, the beneficial effects of the present invention are: a) This invention utilizes the differential feeding method, the gaps in the metal ground plane, and the rectangular defects to form a symmetric electric field distribution in the gaps and rectangular defects, thereby effectively suppressing the common-mode signal due to phase cancellation. The common-mode reflection coefficient is below -2dB throughout the entire frequency band.

[0012] b) The present invention etches gaps on a metal ground plane and achieves multi-band resonant excitation through electromagnetic coupling between the gaps, and can work stably in communication frequency bands such as 3.8GHz, 6.9GHz, 9.6GHz, 12.5GHz and 14.6GHz.

[0013] c) This invention has a low profile, simple structure, and is easy to manufacture. It can be produced using printed circuit board technology. The materials used in its manufacture are only a single-layer dielectric substrate and a copper foil as a metal ground plane. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of the metal grounding plate according to an embodiment of the present invention.

[0015] Figure 2 This is a schematic diagram of the differential microstrip feeder according to an embodiment of the present invention.

[0016] Figure 3 This is a schematic diagram showing the relative positions of the metal ground plane and the differential microstrip feed line in an embodiment of the present invention.

[0017] Figure 4 This is a side view of the overall structure of the present invention.

[0018] Figure 5 This is the main view of the overall structure of the present invention.

[0019] Figure 6 This is the S-parameter curve of the antenna.

[0020] Figure 7 It is the E-plane radiation pattern of the antenna at various operating frequencies.

[0021] Figure 8 It is the H-plane radiation pattern of the antenna at various operating frequencies.

[0022] In the figure: 123, differential microstrip feed line; 1, first metal patch; 2, second metal patch; 3, third metal patch; 456, metal ground plane; 4, rectangular defect segment A; 5, rectangular defect segment B; 6, rectangular defect segment C; 789, zigzag gap; 7, gap a; 8, gap b; 9, gap c; 13, single-layer dielectric substrate. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0024] This embodiment provides a multi-frequency differential antenna with common-mode suppression, which adopts a single-layer dielectric substrate structure and mainly includes three parts: differential microstrip feed line 123, metal ground plane 456 and single-layer dielectric substrate 13.

[0025] The single-layer dielectric substrate 13 is made of FR4 material, which has a dielectric constant of 4.4, a loss factor of 0.02, and a thickness H1 of 0.95 mm.

[0026] The differential microstrip feed line 123 is located on the upper surface of the single-layer dielectric substrate 13 and adopts an n-type symmetrical structure to realize differential signal feeding.

[0027] The metal ground plane 456 is located on the lower surface of the single-layer dielectric substrate 13. It is etched to form symmetrical zigzag gaps 789 and rectangular defect structures to achieve multi-frequency resonance and common-mode suppression.

[0028] like Figure 2 As shown, the differential microstrip feed line 123 consists of three metal patches: The second metal patch 2 and the third metal patch 3 are parallel to each other, each with a length of 8.23 ​​mm and a width of 1.9 mm.

[0029] The first metal patch 1 is connected to the inner side of the second metal patch 2 and the third metal patch 3, with a length of 15mm and a width of 0.66mm, forming an n-shaped structure with the opening facing outward.

[0030] The structure is symmetrical about the central axis a, ensuring symmetrical input of the differential signal.

[0031] like Figure 1 As shown, rectangular defects and two sets of symmetrical zigzag gaps are etched on the metal ground plane 456: 1. Rectangular defect structure

[0032] The rectangular defect consists of three segments. Segment A4 of the rectangular defect has a size of 7.9mm × 7.2mm and is located in the projection area of ​​the differential microstrip feed line 123 on the metal ground plane 456.

[0033] Rectangular defect segment B5: 5mm × 2.75mm in size, one end of which is connected to the middle of the wide side of rectangular defect segment A4, and the other end is connected to the middle of the long side of rectangular defect segment C6, perpendicular to segment C.

[0034] Rectangular defect C segment 6: 19.6mm × 1.1mm in size, symmetrically arranged along the central axis a, with two sets of broken line gaps 789 connected at both ends.

[0035] 2. Zigzag slot structure

[0036] Each set of zigzag seams 789 is composed of three seams connected sequentially: Gap a7: 12.9mm in length and 0.8mm in width, perpendicularly connected to rectangular defect segment C 6.

[0037] Gap b8: 8.8mm in length and 0.8mm in width, perpendicular to gap a7.

[0038] Gap c9: 1mm in length and 0.8mm in width, perpendicular to gap b8, and its distance from the central axis a is less than the distance between gap a7 and the central axis a.

[0039] Two sets of zigzag gaps 789 are symmetrically distributed, with their inner ends connected to the two ends of rectangular defect segment C 6, forming an electromagnetic coupling path to excite multi-frequency resonance.

[0040] This embodiment achieves common-mode signal suppression through a dual mechanism of symmetrical structural design and electromagnetic coupling suppression. Multi-frequency operation is achieved by using a rectangular defect symmetrical about the central axis and two sets of zigzag gaps 789 on the differential feed excitation ground plane. The specific principle is as follows: The upper differential microstrip feed line 123 is symmetrically distributed along the central axis, and the etched gaps in the lower metal ground plane 456 also maintain the symmetry along the central axis. This symmetrical structure ensures that when a common-mode signal (with the same amplitude and phase) is input from both ports of the differential microstrip feed line 123, the signal reaches position a on the central axis along the symmetrical path during transmission. After the equal amplitude and in-phase signals are superimposed, they cancel each other out. At this time, the electric field intensity at the central axis a approaches zero, which cannot satisfy the boundary conditions for gap excitation, thus achieving the common-mode signal suppression effect.

[0041] For differential-mode signals (same amplitude, opposite phase), the symmetrical differential microstrip feed line 123 forms a reverse electric field distribution on both sides of the slot, generating a significant potential difference at the edge of the slot. This excites slot resonance through electromagnetic coupling, resulting in efficient signal radiation.

[0042] The width of the differential microstrip feed 123 is crucial to the matching performance by changing the characteristic impedance and electromagnetic coupling strength. Variations in the width of the differential microstrip feed 123 change the coupling area with the underlying slot: when the width increases, the area directly opposite the differential microstrip feed 123 and the slot increases, mutual capacitance is improved, electromagnetic coupling efficiency of differential mode signals is enhanced, and impedance bandwidth can be broadened; however, excessive width can lead to edge field diffusion, introducing parasitic radiation, which in turn reduces the common-mode rejection effect.

[0043] The gap width primarily affects the common-mode rejection effect through electric field distribution and resonance characteristics. As the gap width W increases, the potential difference cancellation effect of the common-mode signal at the gap edge becomes more significant. However, an excessively wide gap will reduce the Q value, leading to a decrease in gain. A compromise solution is adopted in practical designs.

[0044] Figure 6 The antenna's S-parameter curves show that its bandwidths at various operating frequencies are 3.4-4.3GHz, 6.6-7.2GHz, 9.3-9.9GHz, 12.1-12.9GHz, and 14.2-15.1GHz, respectively. The antenna's common-mode reflection coefficient is less than -2dB across the entire frequency band.

[0045] Figure 7-8The antenna's E / H plane radiation patterns at operating frequencies of 3.8 GHz, 6.9 GHz, 9.6 GHz, 12.5 GHz, and 14.6 GHz are stable across all frequency bands. The common-mode suppression mechanism ensures the stability of the main lobe shape by blocking common-mode radiation components, preventing common-mode signals from breaking the symmetry of the antenna's radiation field and causing the main lobe of the radiation pattern to become concave, shifted, or split.

[0046] The above is just one example. To obtain multi-frequency differential antennas with common-mode suppression at different center frequencies, different parameters can be adjusted according to the specific implementation method to achieve different operating frequency bands.

[0047] It should be understood that the above description of specific embodiments of the present invention is merely an exemplary description provided to facilitate understanding of the present invention by those skilled in the art, and does not imply that the scope of protection of the present invention is limited to these specific examples. Those skilled in the art can obtain more specific embodiments without any creative effort by combining technical features, replacing some technical features, adding more technical features, etc., of the various examples listed in the present invention, provided that they have a full understanding of the technical solutions of the present invention. All of these specific embodiments are within the scope of the claims of the present invention, and therefore, these new specific embodiments should also be within the scope of protection of the present invention.

Claims

1. A multi-frequency differential antenna with common-mode suppression, comprising a differential microstrip feed line (123), a metal ground plane (456), and a single-layer dielectric substrate (13). The differential microstrip feed line (123) and the metal ground plane (456) are located on the upper and lower surfaces of the monolayer dielectric substrate (13), respectively. The metal ground plate (456) has a zigzag gap (789) and a rectangular defect; wherein the rectangular defect includes rectangular defect segment A (4), rectangular defect segment B (5) and rectangular defect segment C (6) that are connected in sequence and symmetrical about the central axis a. The zigzag gap (789) is provided in two sets, and the two sets of zigzag gaps (789) are symmetrical about the central axis a; the inner ends of the two sets of zigzag gaps (789) are respectively connected to the two ends of the rectangular defect segment C (6); The differential microstrip feed line (123) is an n-type structure; the rectangular defect segment A (4) is located in the projection of the region enclosed by the n-type structure onto the metal ground plane (456); The inner end of rectangular defect segment B (5) is connected to the middle of the long side of rectangular defect segment C (6), and the outer end of rectangular defect segment B (5) is connected to the middle of the wide side of rectangular defect segment A (4). Rectangular defect segment B (5) and rectangular defect segment C (6) are perpendicular to each other, and the long side of rectangular defect segment C (6) and the wide side of rectangular defect segment A (4) are parallel.

2. A multi-frequency differential antenna with common-mode suppression according to claim 1, characterized in that, The differential microstrip feed line (123) is symmetrical about the central axis a, and includes a first metal patch (1), a second metal patch (2) and a third metal patch (3); wherein the second metal patch (2) and the third metal patch (3) are parallel to each other, and the first metal patch (1) is connected to the same side of the second metal patch (2) and the third metal patch (3) to form an n-shaped structure, with the opening of the n-shaped structure facing outward.

3. A multi-frequency differential antenna with common-mode suppression according to claim 1, characterized in that, The zigzag gap (789) includes gap a (7), gap b (8) and gap c (9) connected in sequence; gap a (7) is connected to the rectangular defect segment C (6) and is perpendicular to each other; Slits a (7) and b (8) are perpendicular to each other; slits b (8) and c (9) are perpendicular to each other; slits a (7) and c (9) are both parallel to the central axis a, and the distance between slit c (9) and the central axis a is less than the distance between slit a (7) and the central axis a.

4. A multi-frequency differential antenna with common-mode suppression according to claim 1, characterized in that, The single-layer dielectric substrate (13) uses FR4 with a dielectric constant of 4.4 and a loss factor of 0.02.

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